Geo,
While I wouldnt shoot any HTL or steel shot through a fine double (or any heavy load, for that matter), these loads are safe pressures for modern guns and Ive yet to scratch a barrel or choke with them. They are loaded in thick hulls designed for htl and steel shot and each load is wrapped in a mylar sheet for further breakthrough protection. My single-shots guns, while inexpensive, are made of modern steel with chromed barrels and are no more throw away barrels than the barrel of my SBE unless one considers the barrel of a $1500 auto disposable. I have read and seen photos of impressive patterns of Tungsten 9s shot through Savage 219, 220A and B 20 gauges with factory chokes. I shot a lighter load 1 5/16 oz. load of TSS 9s through my 20. 1096 fps, 11,544 psi, with 139 shot inside the 10 ring and 185 inside the 10 to 20 ring. Knowing you have the same gun, I thought youd be interested. This will dispatch any turkey inside of ethical ranges and beyond. The below turkey photos were of a season ending bird (today) of a buddy who shoots the 13/16 oz TSS 9 load through his Mossy 500 .410. Shot at 33 yards. 11 3/4 beard, 1 5/8 spurs, 19 lbs. on a heavily hunted public area. This is his 18th bird with the 13/16 oz. .410 load. He used old school callsslate turtle shell and a wingbone call I made for him. Bear in mind, this guy could call up and kill a turkey in a Kmart parking lot with a pea shooter.
In cleaning the bird, he found 4 nickle-plated #2 shot. One in the thigh joint, 2 in a wing joint and one against the breast bone.
[img]http://i106.photobucket.com/albums/m278/photo205/013_zps5e91c287.jpg[img/]